1. Field of the Invention
This invention is related to the field of wireless devices and, more particularly, to desense problems in wireless devices.
2. Description of the Related Art
Many electronic devices include wireless communications capabilities. Wireless communication is critical for many portable devices such as cell phones, personal digital assistants, global position system (GPS) devices, laptops, and smart phones. Other, less portable devices often include wireless communication as well (e.g. desktop computers and other relatively fixed-location devices).
Wireless communication involves receiving/transmitting a radio-frequency signal or signals on an antenna, and processing the signals to determine the information transmitted. Some devices may include the capability to communicate concurrently over multiple wireless communications protocols (e.g. concurrent communication on wireless fidelity (WiFi); cell phone protocols such as global system for mobile communications (GSM), code division multiple access (CDMA), time division multiple access (TDMA) etc.; Bluetooth; and/or GPS). An issue that such devices can experience is “desense.”Desense refers to system noise that reduces the sensitivity of the antennas for receiving wireless signals. More specifically, desense is a result of a reduction in the signal to noise ratio at the frequency band of interest (i.e. the frequency band, or bands, in use for wireless communication). When desense occurs, the performance of the wireless communication may decrease. In more extreme cases, the wireless communication can cease to operate.
All electronic devices need to meet certain electromagnetic interference (EMI) specifications. Some devices implement data scrambling to modify data streams transmitted between components in the device to make the modified data streams appear to be pseudo random. For example, devices that generate repetitive data patterns in their data streams (such as display data for a display on the device or connected to the device) may implement scrambling of the repetitive data. The scrambling reduces the amplitude of the noise at any given frequency but spreads the noise over a wider band of frequencies. The reduced noise amplitudes help meet the EMI requirements. However, such techniques increase the desense problem by ensuring that any frequency that might be used for wireless communication will likely experience at least some noise.